The present invention relates to a method and a device for identifying the authenticity of paper sheets comprising paper money, and more particularly relates to identification using optically detected data.
When determining the authenticity of paper money, for example, light is radiated across the paper money, and permeated light and reflected light are extracted. Sampling data are obtained from the extracted light, and the sampling data is compared with reference data which has been set beforehand.
A single-wavelength light source is normally used, but when determining the authenticity of paper money using such a light source, it is not possible to determine the authenticity of paper money which has been reproduced on a sophisticated color copier.
The present invention has been conceived in order to solve the above problem, and aims to provide a method and a device capable of high-precision identification of a color-copied paper sheet, without increasing the amount of data extracted therefrom.
In order to achieve the above goals, the present invention provides
(1) a method for identifying a paper sheet, comprising the steps of radiating at least two lights having different wavelengths onto the paper sheet, and detecting light which has permeated therethrough or been reflected therefrom; detecting a change in direction of the strength of the detected light, and producing coded data; and identifying the authenticity of the paper sheet by comparing the coded data with predetermined reference data; and
(2) a device for identifying paper sheets, comprising a carrying unit which conveys a paper sheet along a predetermined path; a radiation unit, provided near the carrying unit and having a switching unit which selectively operates at least two lights having different wavelengths and a light source thereof, the radiation unit sequentially radiating the light from the light source onto the paper sheet being conveyed on the carrying unit; a signal producing unit which converts light permeated through the paper sheet, and light reflected from the paper sheet, to a signal, the light having been detected after being radiated onto the paper sheet by the radiation unit; a change detection unit which codes a change in direction of the strength of the signal from the signal producing unit, and produces detected data therefrom; and a determination unit which has predetermined reference data, and determines the authenticity of the paper sheet by comparing the detected data from the change detection unit with the reference data.